In order to troubleshoot this issue we'll need some more specific information - e.g. which listing you are attempting to claim.
Please contact our Customer Support team either by phone at 888-466-3501 Monday - Friday 7am to 4pm PST, or by email via http://www.trulia.com/help/ask/ to help you.
-Kim, Community Manager
If your home is listed by an agent you should not try to claim it. That would interfere with their ability to enhance your listing. If you are listed as a FSBO, contact the company that placed you in MLS for assistance.